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Extracting Fractional Regional Ventilation in Mice

N Mistry

N Mistry1*, C Badea2, R Gullapalli1, Z Vujaskovic1, W D'Souza1, (1) University of Maryland School of Medicine, Baltimore, MD, (2) Duke University, Durham, NC

WE-G-134-8 Wednesday 4:30PM - 6:00PM Room: 134

Purpose: Testing altered treatment paradigms, prospectively in cohorts of patients remains challenging due to the large variability in tumor characteristics and underlying comorbidities. Preclinical models of lung cancer can enable such studies in a controlled environment. In this work, we wanted to test the feasibility of extracting quantitative fraction regional ventilation (FRV) in small animals.

Methods: Imaging was carried out using a dual source micro-CT system developed to enable high-resolution dynamic images. Mice were anesthetized and mechanically ventilated using a fixed volume (0.4 ml) ventilator. Images were acquired at two phases of ventilation: full inhale breath hold and end-exhale breath hold. Images were spatially matched using deformable image registration from an Image Registration Toolkit. The spatially aligned bi-phasic images (end-inhale and end-exhale) were used to extract FRV by applying a mass correction that is estimated using the ratio of the global inhale-mass and end-exhale mass. A distribution of the FRV values is used to estimate a global ratio of tidal volume (TV) to functional residual capacity (FRC).

Results: Preliminary results indicate that it is feasible to extract fractional regional ventilation in small animals without the use of exogenous gases. Mice that were mechanically ventilated indicate a good correspondence between the mass-corrected FRV based tidal volume (0.402 ml and 0.36 ml) and global ventilated tidal volume (0.4 ml). The mean of the distribution of FRV that is indicative of the global TV/FRC was ~0.6 for both mice.

Conclusion: Earlier studies in small animal imaging have focused on extracting whole lung volumes as a measure of ventilation using micro-CT. This is the first study to test the feasibility of extracting fractional regional ventilation in mice using micro-CT. Early results indicate a good correlation between inhaled tidal volume and tidal volume estimates from FRV.

Funding Support, Disclosures, and Conflict of Interest: National Institute of Biomedical Imaging and Bioengineering (NIBIB) as one of the national Biomedical Technology Resource Centers (P41 EB015897)

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